The present invention relates generally to improvements in embolic protection systems and methods. In particular, it relates to an improved system and method for enabling an embolic protection device to be efficiently and conveniently compressed and retained in compressed condition so as to cross a stenosis in a low profile and be delivered through the patient's vasculature to a location distal to the site of an interventional procedure, without a sheath extending about the filter device. The system also enables the device to be effectively released from compression thereof at the location distal to the interventional procedure site, for enabling expansion and deployment of the filter device for capturing embolic material.
The systems and methods of the present invention are particularly useful when performing balloon angioplasty, stenting procedures, laser angioplasty or atherectomy in critical vessels, such as the carotid, renal, and saphenous vein graft arteries, where the release of embolic debris into the bloodstream could possibly occlude the flow of oxygenated blood to the brain or other vital organs which can cause devastating consequences to the patient.
A variety of non-surgical interventional procedures have been developed over the years for opening stenosed or occluded blood vessels in a patient caused by the build up of plaque or other substances on the walls of the blood vessel. Such procedures usually involve the percutaneous introduction of the interventional device into the lumen of the artery, usually through a catheter. One widely known and medically accepted procedure is balloon angioplasty in which an inflatable balloon is introduced within the stenosed region of the blood vessel to dilate the occluded vessel. The balloon catheter is initially inserted into the patient's arterial system and is advanced and manipulated into the area of stenosis in the artery. The balloon is inflated to compress the plaque and press the vessel wall radially outward to increase the diameter of the blood vessel.
Another procedure is laser angioplasty which utilizes a laser to ablate the stenosis by super heating and vaporizing the deposited plaque. Atherectomy is yet another method of treating a stenosed blood vessel in which a cutting blade is rotated to shave the deposited plaque from the arterial wall. A vacuum catheter may be used to capture the shaved plaque or thrombus from the blood stream during this procedure.
In another widely practiced procedure, the stenosis can be treated by placing a device known as a stent into the stenosed region to hold open and sometimes expand the segment of the blood vessel or other arterial lumen. Stents are particularly useful in the treatment or repair of blood vessels after a stenosis has been compressed by percutaneous transluminal coronary angioplasty (PTCA), percutaneous transluminal angioplasty (PTA) or removal by atherectomy or other means. Stents are usually delivered in a compressed condition to the target site, and then are deployed at the target location into an expanded condition to support the vessel and help maintain it in an open position.
In the past, stents typically have fallen into two general categories of construction. The first type of stent is expandable upon application of a controlled force, often through the inflation of the balloon portion of a dilatation catheter which, upon inflation of the balloon or other expansion means, expands the compressed stent to a larger diameter to be left in place within the artery at the target site. The second type of stent is a self-expanding stent formed from, for example, shape memory metals or super-elastic nickel-titanum (NiTi) alloys, which will automatically expand from a compressed state when the stent is advanced out of the distal end of the delivery catheter into the body lumen. Such stents manufactured from self-expandable materials allow for phase transformations of the material to occur, contributing to the expansion and contraction of the stent.
The above non-surgical interventional procedures, when successful, avoid the necessity of major surgical operations. However, there is one common problem associated with all of these non-surgical procedures, namely, the potential release of embolic debris into the bloodstream which can occlude distal vasculature and cause significant health problems to the patient. For example, during deployment of a stent, it is possible that the metal struts of the stent can cut into the stenosis and shear off pieces of plaque which become embolic debris that can travel downstream and lodge somewhere in the patient's vascular system. Pieces of plaque material can sometimes dislodge from the stenosis during a balloon angioplasty procedure and become released into the bloodstream. Additionally, while complete vaporization of plaque is the intended goal during a laser angioplasty procedure, particles are not always fully vaporized and may enter the bloodstream.
When any of the above-described procedures are performed for example in the carotid arteries, the release of emboli into the circulatory system can be extremely dangerous to the patient. Debris that is carried by the bloodstream to distal vessels of the brain may cause these cerebral vessels to occlude, resulting in a stroke, and in some cases, death. Therefore, although carotid percutaneous transluminal angioplasty has been performed in the past, the number of procedures performed has been limited due to the justifiable fear of causing an embolic stroke should embolic debris enter the bloodstream and block vital downstream blood passages.
Medical devices have been developed to attempt to deal with the problem created when debris or fragments enter the circulatory system following treatment utilizing any one of the above-identified procedures. One approach which has been attempted is the cutting of any debris into minute sizes which pose little chance of becoming occluded in major vessels within the patient's vasculature. However, it is often difficult to control the size of the fragments which are formed, and the potential risk of vessel occlusion still exists, making such procedures in the carotid arteries a high-risk proposition.
Other techniques which have been developed to address the problem of removing embolic debris include the use of catheters with a vacuum source which provides temporary suction to remove embolic debris from the bloodstream. However, as mentioned above, there have been complications with such systems since the vacuum catheter may not always remove all of the embolic material from the bloodstream, and a powerful suction could cause problems to the patient's vasculature.
Further techniques which have had some limited success include the placement of an embolic protection device such as a filter or trap downstream from the treatment site to capture embolic debris before it reaches the smaller blood vessels downstream. Such embolic protection devices enable the filtering of embolic debris which may be released into the bloodstream during the treatment to the vessel, and yet allow a sufficient amount of oxygenated blood to flow past the device to supply vital organs downstream from the treatment site.
However, there have been problems associated with filtering systems, particularly during the insertion, expansion, deployment, and removal of the filter within the blood vessel. The filter needs to cross the stenosis in as small a profile as possible so as to clear the stenosis and prevent damage thereto. Previous designs have employed an outer catheter called a “sheath” to keep these filters constrained prior to delivery beyond the stenosis. This outer catheter necessarily increases the profile of the device which could in and of itself create embolic complications as this high profile device is forced through the stenosis. After crossing the stenosis and being positioned distal to the interventional procedure site, the filter needs to be deployed, and after the interventional procedure has been performed, the filter needs to be removed with the captured embolic material therein, in an efficient and effective manner.
Therefore, the present invention provides improved systems and methods for treating stenosis in blood vessels which reduces the profile and improves the stenosis crossing characteristics of a filter, for crossing the stenosis to a position distal to the interventional procedure site for deployment of the filter. It also enables effective filter deployment at the position distal to the interventional procedure site, and removal from the position distal to the interventional procedure site, for capturing embolic debris in the bloodstream that can cause blockage in vessels at downstream locations. The improved systems and methods of the present invention further enable filtering of embolic debris which may be released into the bloodstream during the treatment to the vessel, and allow a sufficient amount of oxygenated blood to flow past the filtering device to supply vital organs downstream from the treatment site. Moreover, the systems and methods are relatively easy for a physician to use, while enabling the effective delivery and recover of a filtering system capable of removing embolic debris released into the bloodstream. The inventions disclosed herein satisfy these and other needs.